One type of work machine is an agricultural combine. Agricultural combines are engine powered machines that harvest, thresh, separate and clean an agricultural crop. The resulting clean grain is stored in a grain tank located on the combine. The clean grain can then be transported from the grain tank to a truck, grain cart or other receiving bin by an unloading auger.
Agricultural combines have several rotating shafts (e.g., rotor, clean grain elevator, etc.) that are monitored for changes in speed. Typically, a large table is maintained that indicates the allowed speed range for each shaft based on machine type and other customer settings. When the shaft speed falls below the value as defined in this table, a low shaft speed alarm is activated to notify the operator.
However, with this approach, with every change in machine settings and options, the table becomes more difficult to maintain. Also, an operator may experience the occasional nuisance alarm when nothing is wrong.